In the semiconductor field it is common to sequentially grow several different layers of semiconductor material and use various masks and etching steps to form the desired devices and terminals on the devices. In some methods, masking material. e.g. photoresist, dielectric layer, or the like, is applied and semiconductor material is grown over masked and unmasked areas. The material on the masked areas is then removed by etching and lift-off.
In each of these prior art methods of fabricating semiconductor devices, etching is required to remove unwanted material. During the etching process, the material of the semiconductor device has a high likelihood of being contaminated by the etchant, which contamination greatly reduces the life of the device, the operating characteristics of the device, and the reliability of the device. Also, various layers of the semiconductor devices have different etch rates, so that the etching process is very nonuniform. Further, the etching process severely damages semiconductor material adjacent the etched areas which further reduces life, operating characteristics, and reliability. Also, etching processes are very time consuming and difficult to perform.
In addition to the etching problems, all known prior art fabrication processes require many interspersed growing, masking and etching steps which greatly complicate and lengthen the process. For example, when epitaxial layers are grown, the wafers must be placed in a vacuum or pressure chamber to provide the atmosphere for the growth. Each time the wafer must be etched and/or masked, it must be removed from the chamber, resulting in large amounts of preparation time for each step. Also, each time wafers are removed from a chamber and subsequently replaced, the opening and preparation of the chamber (as well as the processing of the wafer) is an opportunity for additional impurities and contaminants to be introduced to the wafer.
Accordingly, it would be highly desirable to provide fabrication methods for semiconductor devices which do not require etching and/or placing wafers in a processing chamber and removing them several times in sequence.
It is a purpose of the present invention to provide a new and improved method of fabricating semiconductor devices.
It is another purpose of the present invention to provide a new and improved method of fabricating semiconductor devices which does not require etching the semiconductor material to form devices.
It is still another purpose of the present invention to provide a new and improved method of fabricating semiconductor devices which does not require the introduction and removal of wafers from processing chambers several times in sequence.
It is a further purpose of the present invention to provide a new and improved method of fabricating semiconductor devices which is much simpler and includes less chance of contamination of the devices.
It is a still further purpose of the present invention to provide new and improved semiconductor devices which lend themselves to further integration, and include characteristics that are not achieved by standard processes.